Effect of substrate curvature on microstructure and gas permeability of hollow fiber MFI zeolite membranes

Chen, Chien‐Hua; Meng, Lie; Tung, Kuo‐Lun; Lin, Jerry Y S

doi:10.1002/aic.16197

“…S3, Generally, the thickness of zeolite membranes plays a role in the trade-off between gas permeability and selectivity. Whilst a thin membrane can increase the gas permeability this often leads to a reduction in the selectivity since the formation of defects and cracks is very likely during the synthesis of thin zeolite membranes on the surface of a support, especially cylindrical ones [43,57,58]. The synthesis time is a key factor for SAPO-34 crystallisation, and hence the membrane thickness.…”

Section: As Prepared Sapo-34 Membranes: Characterisation and Performance In Co 2 /Ch 4 Separationmentioning

confidence: 99%

Defects-healing of SAPO-34 membrane by post-synthesis modification using organosilica for selective CO2 separation

Mu

¹

,

Chen

²

,

Xiang

³

et al. 2019

Journal of Membrane Science

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It is challenging to avoid the formation of defects in zeolite membranes during their preparation.Herein, we present a facile vacuum-assisted deposition (VAD) method as a feasible solution to address this challenge. Defective SAPO-34 membranes supported on tubular porous alumina were healed using bis(triethoxysilyl)ethane (BTESE)-derived organosilica via VAD and these showed an improved performance in the selective CO 2 separation from an equimolar CO 2 /CH 4 mixture. Specifically, by controlling the amount of organosilica deposited, the coating was able to heal the non-selective defects in SAPO-34 membranes without compromising the CO 2 permeance, but increased the CO 2 /CH 4 selectivity notably (by a factor of ca. 2.5 at 25 °C and 200 kPa). An excessive coating of organosilica by VAD resulted in a thick layer on top of the SAPO-34 membrane which led to a significant decrease in the CO 2 permeance. Additionally, a modified membrane was also investigated for the CO 2 /CH 4 gas feed with different CO 2 concentrations from 20-50 mol.% and this showed that a relatively concentrated CO 2 in the system could also be improved in terms of its separation performance.

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“…[14b, 15b] In unary permeation, the membrane (particularly after tertiary treatment) shows very high n-butane selectivity and permeance.T his clearly indicates the excellent microstructural quality of the membrane. An exact comparison of separation factors between two selective membrane types may have only limited value,b ut possible reasons for the difference include the hydrothermal growth mechanisms (for example,delivery of silica reactants from support versus from liquid phase as well as the SDAs), different microstructures after calcination of curved (fiber) versus flat (disk) membranes, [16] and different measurement times. Theresults of the present work with previous reports of MFI membranes (made by conventional polycrystalline film growth as well as with 2D MFI nanosheets) and other membrane types (polymeric,m ixed matrix, ZIF) are compared in the Supporting Information, Table S2.…”

Section: Angewandte Chemiementioning

confidence: 99%

“…75 after 60 h). An exact comparison of separation factors between two selective membrane types may have only limited value,b ut possible reasons for the difference include the hydrothermal growth mechanisms (for example,delivery of silica reactants from support versus from liquid phase as well as the SDAs), different microstructures after calcination of curved (fiber) versus flat (disk) membranes, [16] and different measurement times. [15] Finally,w e extend our investigation to the removal of natural gas liquid (NGL) components such as n-butane and propane from methane,currently carried out by cryogenic distillation.…”

Section: Angewandte Chemiementioning

confidence: 99%

Continuous Zeolite MFI Membranes Fabricated from 2D MFI Nanosheets on Ceramic Hollow Fibers

Min

¹

,

Yang

²

,

Korde

³

et al. 2019

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High-quality 2D MFI nanosheet coatings were prepared on a-alumina hollowf iber supports by vacuum filtration and then transformed into molecular sieving membranes by two sequential hydrothermal treatments.T his processing method eliminates the need for specially engineered silica-based support materials that have so far been necessary to allow the formation of functional membranes from 2D MFI nanosheets.T he sequential steps enhance adhesion of the membrane on the fiber support, fill in nanoscale gaps between the 2D nanosheets,a nd preserve the desirable (0k0) out-ofplane orientation without the need of any support engineering or modification. The membrane exhibits high performance for separation of n-butane from i-butane,a nd for other technologically important hydrocarbon separations.T he present findings have strong implications on strategies for obtaining thin, highly selective zeolite membranes from 2D zeolites in atechnologically scalable manner.Membrane-based separations have high potential for energy efficiency and cost reduction in chemical processes. Inorganic molecular sieving zeolite membranes [1] can offer anumber of advantages,such high permeability and selectivity as well as excellent thermal and chemical stability,inmany applications.However,the difficulty of low-cost and scalable fabrication of zeolite membranes is ak ey barrier to their widespread application. In the last few years,t he emergence of zeolitic membranes based upon two-dimensional (2D) zeolite nanosheets [2] has created an opportunity to overcome this barrier.Inprinciple,uniform and thin (0.1-1 mm) coatings of high-aspect ratio zeolite nanosheets can be deposited on nearly any kind of porous membrane substrate and then perform af inal zeolite growth step to close the nanoscopic gaps between the nanosheets,thereby creating very high-flux molecular sieving membranes.F or example,n anosheets (3-5nminthickness) of zeolite MFI have been synthesized both by exfoliation of 2D MFI layered stacks [2a, 3] as well as by seedassisted bottom-up methods. [2b] TheM FI nanosheets produced by the latter route offer particularly attractive structural features,s uch as av ery high aspect ratio favorable for thin coatings,v ery short diffusion pathways through the nanosheet, high-yield production without need for an exfoliation process,a nd good dispersibility in water. MFI membranes fabricated from these MFI nanosheets have shown high fluxes and excellent separation of xylene isomers and also of butane isomers. [2b, 4] Despite the excellent separation performance of the above MFI membranes,t heir current fabrication process faces considerable hurdles in practical feasibility and scalability.Atpresent the fabrication process is only possible on porous Stçber silica-derived disk-type supports.I th as been hypothesized that such as upport provides an optimal delivery of silicate reactants to the 2D MFI nanosheet coating and facilitates its growth into adefectfree membrane,a nd its properties are difficult to replicate with other types of silica-cont...

show abstract

“…75 after 60 h). An exact comparison of separation factors between two selective membrane types may have only limited value, but possible reasons for the difference include the hydrothermal growth mechanisms (for example, delivery of silica reactants from support versus from liquid phase as well as the SDAs), different microstructures after calcination of curved (fiber) versus flat (disk) membranes, and different measurement times . Finally, we extend our investigation to the removal of natural gas liquid (NGL) components such as n ‐butane and propane from methane, currently carried out by cryogenic distillation .…”

Section: Figurementioning

confidence: 99%

Continuous Zeolite MFI Membranes Fabricated from 2D MFI Nanosheets on Ceramic Hollow Fibers

Min

¹

,

Yang

²

,

Korde

³

et al. 2019

View full text Add to dashboard Cite

High-quality 2D MFI nanosheet coatings were prepared on a-alumina hollowf iber supports by vacuum filtration and then transformed into molecular sieving membranes by two sequential hydrothermal treatments.T his processing method eliminates the need for specially engineered silica-based support materials that have so far been necessary to allow the formation of functional membranes from 2D MFI nanosheets.T he sequential steps enhance adhesion of the membrane on the fiber support, fill in nanoscale gaps between the 2D nanosheets,a nd preserve the desirable (0k0) out-ofplane orientation without the need of any support engineering or modification. The membrane exhibits high performance for separation of n-butane from i-butane,a nd for other technologically important hydrocarbon separations.T he present findings have strong implications on strategies for obtaining thin, highly selective zeolite membranes from 2D zeolites in atechnologically scalable manner.Membrane-based separations have high potential for energy efficiency and cost reduction in chemical processes. Inorganic molecular sieving zeolite membranes [1] can offer anumber of advantages,such high permeability and selectivity as well as excellent thermal and chemical stability,inmany applications.However,the difficulty of low-cost and scalable fabrication of zeolite membranes is ak ey barrier to their widespread application. In the last few years,t he emergence of zeolitic membranes based upon two-dimensional (2D) zeolite nanosheets [2] has created an opportunity to overcome this barrier.Inprinciple,uniform and thin (0.1-1 mm) coatings of high-aspect ratio zeolite nanosheets can be deposited on nearly any kind of porous membrane substrate and then perform af inal zeolite growth step to close the nanoscopic gaps between the nanosheets,thereby creating very high-flux molecular sieving membranes.F or example,n anosheets (3-5nminthickness) of zeolite MFI have been synthesized both by exfoliation of 2D MFI layered stacks [2a, 3] as well as by seedassisted bottom-up methods. [2b] TheM FI nanosheets produced by the latter route offer particularly attractive structural features,s uch as av ery high aspect ratio favorable for thin coatings,v ery short diffusion pathways through the nanosheet, high-yield production without need for an exfoliation process,a nd good dispersibility in water. MFI membranes fabricated from these MFI nanosheets have shown high fluxes and excellent separation of xylene isomers and also of butane isomers. [2b, 4] Despite the excellent separation performance of the above MFI membranes,t heir current fabrication process faces considerable hurdles in practical feasibility and scalability.Atpresent the fabrication process is only possible on porous Stçber silica-derived disk-type supports.I th as been hypothesized that such as upport provides an optimal delivery of silicate reactants to the 2D MFI nanosheet coating and facilitates its growth into adefectfree membrane,a nd its properties are difficult to replicate with other types of silica-cont...

show abstract

Effect of substrate curvature on microstructure and gas permeability of hollow fiber MFI zeolite membranes

Cited by 26 publications

References 37 publications

Defects-healing of SAPO-34 membrane by post-synthesis modification using organosilica for selective CO2 separation

Defects-healing of SAPO-34 membrane by post-synthesis modification using organosilica for selective CO2 separation

Continuous Zeolite MFI Membranes Fabricated from 2D MFI Nanosheets on Ceramic Hollow Fibers

Continuous Zeolite MFI Membranes Fabricated from 2D MFI Nanosheets on Ceramic Hollow Fibers

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